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Energy Performance Ratings for Windows & Doors and What They Mean

Window Energy RatingsWhen you’re shopping for new windows or doors, there’s a lot to pay attention to. Something you’re sure to see, but probably unsure exactly what it means, are the performance ratings on the labels. This can be confusing for many homeowners, but it’s definitely something that’s worth your time becoming familiar with. These performance ratings can give you a lot of insight into how the window or door will perform in your home when it comes to energy efficiency. While you may not take that performance aspect of a window or door into mind, a product with a good rating can help you save lots when it comes to your heating and cooling bills year round. All-Weather Window, Doors & Siding sums up the top three energy performance ratings and what they mean for you.

Window Energy Ratings 

The National Fenestration Rating Council (NFRC) operates a program that tests, certifies, and labels windows, doors, and skylights based on their energy performance ratings. The NFRC label provides a reliable way to determine a window’s energy properties and to compare products. You can find these labels on all ENERGY STAR® qualified window, door, and skylight products. ENERGY STAR bases its qualification only on U-factor, solar heat gain coefficient, and air leakage ratings. 

Related Read: 3 Energy-Efficient Window Treatments


This performance rating is based on the rate at which a window, door, or skylight conducts non-solar heat flow. It’s usually expressed in units of Btu/hr-ft2-oF. The lower the U-factor, the more energy-efficient the window, door, or skylight.

Solar Heat Gain Coefficient

This performance rating is also seen abbreviated as SHGC, and i
s the fraction of solar radiation admitted through a window, door, or skylight. The lower the SHGC rating, the less solar heat it transmits and the greater its ability to provide shade. A product with a high SHGC rating is more effective at collecting solar heat during the winter. A product with a low SHGC rating is more effective at reducing cooling loads during the summer by blocking heat gain from the sun. Which type of SHGC rating you look for in products for your home should depend on your home’s climate, orientation, and external shading, as well as the climate of the area where you live. Arizona homes, for instance would likely look for windows and doors with a low SHGC rating, while a home in Minnesota might look for products with higher SHGC ratings.

Air Leakage

No one likes drafty doors or windows. This performance rating will give you a good idea how airtight a door, window, or skylight is. It measures the rate of air movement around a window, door, or skylight. It’s expressed in units of cubic feet per minute per square foot of frame area (cfm/ft2). A product with a low air leakage rating is tighter, and less likely to become drafty than one with a high air leakage rating.

For more information on how energy-efficient windows and doors can help you save, call your trusted home experts at All-Weather Window, Doors & Siding at 913-262-4380.

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